Composite cycle turbomachinery

ABSTRACT

1. A composite fluid flow turbomachine comprising: A FIRST COMPRESSOR; A SECOND COMPRESSOR, SAID SECOND COMPRESSOR BEING ARRANGED TO CONTINUOUSLY RECEIVE A PART ONLY OF THE FLOW FROM SAID FIRST COMPRESSOR, AN INNER DUCT SURROUNDING SAID SECOND COMPRESSOR; AN OUTER DUCT SURROUNDING SAID FIRST COMPRESSOR AND SAID INNER DUCT; MEANS FOR INJECTING FUEL WITHIN SAID OUTER DUCT AND SAID INNER DUCT FOR SUPPORTING COMBUSTION THEREIN DOWNSTREAM OF SAID FIRST COMPRESSOR AND SAID SECOND COMPRESSOR, RESPECTIVELY; A FIRST POWER TURBINE LOCATED IN SAID INNER DUCT AND RECEIVING AN INTEGRAL FLUID FLOW STREAM FROM SAID FIRST AND SECOND COMPRESSORS; Mach A SECOND POWER TURBINE LOCATED PARTIALLY IN SAID OUTER DUCT, SAID SECOND POWER TURBINE RECEIVING A FLUID FLOW STREAM FROM SAID FIRST COMPRESSOR AND THE INTEGRAL FLUID FLOW STREAM FROM SAID FIRST AND SECOND COMPRESSORS; AN OUTER DRIVESHAFT, SAID FIRST POWER TURBINE AND SAID SECOND COMPRESSOR BEING MOUNTED ON SAID OUTER DRIVESHAFT FOR ROTATION THEREWITH; AN INNER DRIVESHAFT CONCENTRIC TO SAID OUTER DRIVESHAFT, SAID SECOND POWER TURBINE AND SAID FIRST COMPRESSOR BEING MOUNTED ON SAID INNER DRIVESHAFT FOR ROTATION THEREWITH; AND A POWER TRANSFER TURBINE, SAID POWER TRANSFER TURBINE BEING ARRANGED IN SERIES FLOW RELATION WITH SAID FIRST AND SECOND POWER TURBINES, SAID POWER TRANSFER TURBINE BEING MOUNTED ON SAID INNER DRIVESHAFT AND FURNISHING POWER TO HELP DRIVE SAID FIRST COMPRESSOR, WHEREBY THE OVERALL CYCLE EFFICIENCY OF SAID COMPOSITE FLUID FLOW TURBOMACHINE IS INCREASED.

United States Patent Batscha 1 July 18,1972

[ COMPOSITE CYCLE TURBOMACHINERY [72] Inventor: Alexander P. Batscha,Cincinnati, Ohio [73] Assignee: General Electric Company [22] Filed: May31, 1962 21 Appl. No.: 199,191

52 US. Cl ..60/262, 60/263 5 1 Int. Cl ..F02k 1/02 58 Field of Search..60/35.6 0, 35.6 w, 35.6 v,

60/35.6 CC, 39.16, 262, 263; 230/116 A, 116 B Primary Examiner-SamuelFeinberg Attorney-Oscar B. Waddell, G. R. Powers, E. S. Lee, Ill, DerekP. Lawrence, Frank L. Neuhauser and Melvin M. Goldenberg EXEMPLARY CLAIMl A composite fluid flow turbomachine comprising:

a first compressor; 4

a second compressor, said second compressor being arranged tocontinuously receive a part only of the flow from said first compressor,

an inner duct surrounding said second compressor;

an outer duct surrounding said first compressor and said inner duct;

means for injecting fuel within said outer duct and said inner duct forsupporting combustion therein downstream of said first compressor andsaid second compressor, respectively;

a first power turbine located in said inner duct and receiving anintegral fluid flow stream from said first and second compressors;

a second power turbine located partially in said outer duct, said secondpower turbine receiving a fluid flow stream from said first compressorand the integral fluid flow stream from said first and secondcompressors;

an outer driveshaft, said first power turbine and said second compressorbeing mounted on said outer driveshaft for rotation therewith;

an inner driveshaft concentric to said outer driveshaft, said secondpower turbine and said first compressor being mounted on said innerdriveshaft for rotation therewith;

and a power transfer turbine, said power transfer turbine being arrangedin series flow relation with said first and second power turbines, saidpower transfer turbine being mounted on said inner driveshaft andfurnishing power to help drive said first compressor, whereby theoverall cycle efficiency of said composite fluid flow turbomachine isincreased.

7 Clains, 7 Drawing Figures PATENTEUJULIBM 3.671.012

SHEET 1 [1F 2 Elm.

Mfr/1451 PATENTED Jun 8 I972 sum 2 OF 2 INVENTOR. fllfXfl/WEEP. 547.50%

COMPOSITE CYCLE TURBOMACI'IINERY The present invention relates generallyto turbomachinery and, more specifically, to an arrangement ofturbomachinery which acts as a turbofan at subsonic flight conditionsand as a turbojet at supersonic flight conditions.

A well-known type of turbomachine is an aircraft gas turbine engineincluding a duct having an air inlet at one end and an opening at theother end for the exit of exhaust gases. In

such an engine air enters the duct, is compressed by a rotatingcompressor, heated in a combustion chamber, and expanded through aturbine wheel. The power output of the turbine wheel drives thecompressor rotor, which is mounted on the same driveshaft, or anymechanical load connected to the driveshaft. A turbojet may therefore bedefined simply as a gas turbine in which no excess energy (above thatrequired to drive the compressor and any accessories) is supplied by theturbine (wheel) and the available energy in the exhaust gases suppliesthe jet thrust. On the other hand, in a turbofan, which includes a lowpressure compressor or fan, located in an auxiliary duct arrangedannularly about the primary duct, or in a turboprop engine, the turbinedoes provide excess energy over that needed to drive the compressorrotor. The excess energy is used to drive a propeller, in the turboprop,and the fan, or low pressure compressor, in the turbofan.

Any given propulsion cycle will usually prefer a high turbine inlettemperature at low pressure ratios, where pressure ratio is defined asthe ratio of the pressure at the inlet end of the duct to that at thedischarge end of the compressor, in order to obtain a high value of netthrust without augmentation or afterburning. For low net thrust values,on the other hand, the preferred cycle will have a low turbine inlettemperature with a high pressure ratio. However, pressure ratio isproportional to the square root of the turbine inlet temperature anddirectly proportional to the weight of airflow through the compressor.Therefore, in a conventional turbomachine propulsion cycle a low thrustvalue at which both the weight of airflow and the turbine inlettemperature are low results in a very low cycle pressure ratio and,hence, a less efficient machine.

It is also known that generally for aircraft flight missions at greaterthan sonic speeds a turbojet engine with high turbine inlet temperaturegives better performance, whereas at speeds less than sonic the turbofanengine is preferably in terms of performance. It would seemadvantageous, therefore, to combine the advantages of each engine in asingle machine having 4 a propulsion cycle wherein the machine hasturbojet characteristics at Mach 3.0 and above, and, with the aid of asuitable bypass arrangement, turbofan characteristics at less than Mach1.0. I have determined that it is possible to design a convertible orcomposite cycle machine which will provide a lighter machine with ahigher pressure ratio compressor and, moreover, a machine that will burnless fuel per hour per pound of thrust, thus having a lower specificfuel consumption" (SFC), which is an indication of better efi'i ciency.

Thus, a general object of the present invention is to provide aconvertible turbomachine which combines improved performance at flightspeeds of Mach 3.0, and beyond, and at subsonic flight speeds.

A more specific object is to provide a convertible turbomachine whichwill operate more efficiently at off-design points and withoutdiscontinuity between subsonic flight speeds and flight speeds of Mach3.0 and above.

It is also an object of the invention to provide a turbomachine having acomposite, or convertible, propulsion cycle wherein a single unitoperates as a turbojet" at high Mach flight speeds and as a modifiedturbofan at speeds below Mach 1.0.

Briefly, in one embodiment of my invention I provide a composite cycleturbomachine including a first compressor, a second compressorcontinuously receiving pan of the flow from the first compressor, firstand second duct means, the first duct means surrounding the compressorsand the second duct means, means for injecting fuel into each of theduct means for sustaining combustion therein, a first turbine 5 streamfrom the first and second compressors. The invention further includespower transfer turbine in series flow relation with the first and secondturbines and one of the duct means, the power transfer turbine acting toincrease the overall cycle efficiency in either the turbojet" operatingmode, or the turbofan operating mode.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter of the present invention, itis believed that the invention will be better understood, and otheradvantages and objects thereof become more apparent, from the followingdetailed description read in conjunction with the accompanying drawingsin which:

FIGS. la-lc are schematic side views taken parallel to the axis ofseveral turbomachines comprising, respectively, a conventional turbojet,a conventional turbofan, and a machine having a composite cycle asdescribed herein;

FIG. 2 is a graph showing factors optimizing performance of my novelcomposite cycle turbomachine as a turbofan," i.e.,

2 5 at relatively low thrust operation;

FIG. 3 is a graph showing factors optimizing performance of my novelcomposite cycle turbomachine as a turbojet, i.e., at relatively highthrust operation; and

FIGS. 4-5 illustrate alternate arrangements of turbomachine componentsutilizing the composite propulsion cycle of the present invention.

Turning now to FIGS. la-lc, FIG. 10 only will be discussed in detailsince it illustrates the invention and the machines of FIGS. 1a and lbare well known to those skilled in the art, the

nomenclature being generally the same. FIG. 1c discloses a and an outletend 14. Located in the inlet end is a forward, or

low-pressure compressor 20 of axial-flow, multistage design. Just aft ofthis first compressor is located a second, or high pressure axial-flowmultistage compressor 22. While this well known type of compressor hasbeen shown for purposes of illustration it will be understood that othertypes of compressors, e.g., centrifugal, may also be utilized. A portionof the flow from the first compressor will enter the annular space 24formed by the outer duct 10 and a second, smaller duct 26 locatedconcentrically within the former and surrounding the second, or innercompressor. The remainder of the flow from the first compressor entersthe area 28 where it will be drawn into the second compressor. In theinner duct and downstream of the second compressor is located a firstcombustion means 30, including fuel injecting means 32 for supplyingfuel to the duct for supporting combustion therein. In series flowrelation with the first combustion means 30 is a first, or high pressurepower turbine 34. The first power turbine is connected by a shaft 36 tothe second compressor and supplies the energy needed to drive the secondcompressor.

Located downstream of area 24, in the outer duct, is a second combustionmeans 40, also including fuel injecting means 42 for supplying fuel tothe outer duct to support combustion therein. In series flow relationwith this second combustion means is a second, or low pressure powerturbine 44.

This second power turbine, which may also be termed the duct" turbinesince it projects into what is conventionally known as a bypass duct, isconnected to the low pressure compressor by means of a shaft 46 andfurnishes energy to drive the first compressor.

derstood that any or all of the turbines 34, 44, and 50, respectively,may consist of more than one stage, although one turbine wheel only isshown in the illustration.

At Mach 3.0, and above, operation may be likened to that of theconventional turbojet shown in FIG. la. Thus, air is taken into theforward compressor 20 and compressed. It is then heated in the outerduct combustion means 40, expanded through the power turbine 44 andejected to provide thrust. If desired, reheat or afterburner combustionmeans 60 may be provided, for added thrust, along with a variable areajet exhaust nozzle 62. In the case where the inner duct combustion means30 is inoperative, the inner spool, i.e., the interconnectedhigh-pressure compressor 22, shaft 36 and power turbine 34 willwindmill, taking in an insignificant amount of air for ventilationpurposes.

At transonic flight speeds and speeds below Mach 1.0, however, theoperation may be described as that of a turbofan, modified by theaddition of an inner spool which provides added flexibility of operationat off-design points. Assume, a low power or thrust requirement. Withthe outer combustion means 40 inoperative all combustion takes place atthe rela tively higher pressure ratio of the inner combustion system orgas generator. With power so reduced, the pressure ratio of the fan, orforward compressor 20 is also reduced, which raises the corrected speedn/fi n engine speed in rpm relative absolute temperature of of the innerspool," and its pressure ratio, so that the overall propulsion cyclepressure ratio tends to remain constant.

Additionally, with use of the power transfer turbine 50 when operatingas a turbojet with burning taking place in the inner duct combustor 30and at lower power (thrust) requirements, the work of the duct (fan)power turbine 44 can be augmented since some power is derived from thepower transfer turbine. This has an effect which may be described asincreasing the duct turbine efficiency" to a value greater than 1, Le,less pressure is lost (more energy is available) than would be true ifthe outer burner only were operative at this lower thrust mode ofoperation. Part of the increased efficiency is due to the power transferturbine taking out energy to help drive the low pressure compressor 20before the gases in the inner duct are subject to mixing with theairflow in the outer duct.

On the other hand, when operating at higher power (thrust) modes theprovision of the inner gas generator in combination with the powertransfer turbine, makes possible an increase in the power, or energy,available from the main or duct turbine since both turbines help drivethe low pressure compressor. Additionally, operation at high thrustmodes with the outer combustor operative has the effect of reheating theair between the power transfer turbine 50 and the duct turbine 44. Withthe described arrangement it is therefore possible to have a situationwherein the pressure in the tail or exhaust end of the duct tends toapproach the high value available with a high pressure ratio turbojet,while the tail end temperature can approach the high value availablewith a low pressure ratio turbojet. Thus, the composite cycle of thepresent invention allows turboject operation from very high to very lowthrust values while greatly reducing the variation in overall cyclepressure ratio. This results in higher efficiency of operation with aconsequent better SFC. In addition, as shown in dotted lines in FIG. 10,a mixing section indicated generally at 64 may be provided to facilitatethe mixing of the gases in the event operation is such that the outerduct combustion means is turned off and only the inner gas generator isoperative.

The characteristics of the composite cycle of my invention may perhapsbe more clearly understood if we examine the effect of componentarrangement on turbofan characteristics, at low thrust settings, and onturbojet" characteristics at high thrust settings. Reference should bemade to FIGS. 2 and 3 wherein graphs are presented which showindependently some of the factors involved in optimizing performance ofthe composite turbomachine at either high or low thrust requirements.

The curves in FIG. 2 illustrate the composite cycle characteristics atslightly less than Mach 1.0 in terms of SFC for values of correctedengine thrust (gross thrust, in pounds, per unit airflow) at severalvalues of bypass ratio (the ratio of the weight of airflow in the bypassduct to that of the primary inner airflow). Curve A indicates arelatively high bypass ratio while curve C indicates a relatively lowbypass ratio. The left portion of each curve typifies operation with theouter combustion means inoperative and the right portion showsperformance with the outer combustion means operative. It will be notedthat at the higher thrust values, with a lower bypass ratio, better SFC(efficiency) is possible with the composite cycle turbomachine of thepresent invention, since the transfer turbine is furnishing more of theenergy needed to drive the low pressure compressor, or fan." Thus, thefact that the power transfer turbine makes available more energy for thelow pressure ratio cycle, or turbofan" operation, enables the compositeturbomachine to have a better SFC than would be possible with aconventional machine. It will also be noted that at lower thrust levelsof operation the curves A, B, and C cross on the graph, indicating thatthe effect of bypass ratio is reversed and a higher bypass ratio, withits correspondingly lower inlet temperature into the duct turbine, willbe more efficient. The cruise level of thrust for any particular flightmission will therefore be largely determinative of the bypass ratioadopted. It should be pointed out that the composite cycle machineprovides a nearly constant bypass ratio at varying flight speeds, oncethe ratio is adopted for the desired cruise level, which has the furtheradvantage of increasing the composite cycle machine s overallefficiency.

Referring now to FIG. 3, wherein the composite cycle is illustrated interms of its turbojet characteristics, it should be noted that theprimary purpose of the inner spool or gas generator is to furnish powerto the turbojet We can perhaps best show its value to the compositecycle by pointing out that the energy which it furnishes need not befurnished by the duct turbine. Thus, if we include the work furnished tothe cycle by the power transfer turbine, the duct turbine efficiency canbe shown as an equivalent turbine efficiency. In other words, definingturbine efficiency to mean delivered compressor work divided by idealturbine work, the addition of the work furnished by the power transferturbine can make the equivalent efficiency of the duct turbine greaterthan 1. This is shown by the curves in the graph in FIG. 3 for varyingpressure ratios of the forward compressor 20. Curve A indicates arelatively low pressure ratio and curve D a higher pressure ratio. Itwill be noted that, since at the lower forward compressor pressureratios in the composite turbomachine more of the work is furnished bythe power transfer turbine, the equivalent turbine efficiency can bequite high. At higher pressure ratios, of course, the second compressorinlet temperature will reach such values that less work per pound ofairflow is available from the inner or high pressure ratio compressorand, additionally, the work requirement for the forward or low pressureratio compressor rises. These conditions combine to militate against theinner gas generator adding to the duct turbine efficiency.

Finally, it should be noted that even when the forward compressordischarge temperature is high, either as a result of high pressure ratioor high thrust requirements (flight speeds), and work available from thepower transfer turbine decreases, the overall efficiency of thecomposite cycle turbomachine of the present invention will not suffersince at such high flight speeds the cycle is substantially independentof the work capability of the inner gas generator.

FIGS. 4-5 illustrate alternative arrangements of turbomachinerycomponents wherein the machines utilize the composite cycle of thepresent invention. While all the embodiments disclosed herein may betermed mixed flow cycles, wherein the air that is discharged by the lowpressure or forward compressor is drawn off by an inner duct andconveyed to the inlet of a high pressure compressor in the embodimentsof FIGS. 4 and 5 a more compact machine is provided by the direction offlow, as indicated by the arrows in the drawings, being reversed. Fromthe high pressure compressor the air passes through combustion means,from whence the resultant high pressure, high temperature gas isdirected to a power turbine (which drives the high pressure compressor)and then to a power transfer turbine. The gases effluent from the powertransfer turbine then mix with that portion of the low pressurecompressor discharge which was not drawn in by the inner duct and in asubstantially mixed condition these gases pass through an outer duct, asecond combustor (which may or may not supply any heat to the cycle,depending on the operation mode), and from there through a main power(duct) turbine which furnishes that portion of the energy needed todrive the forward compressor which is not furnished by the powertransfer turbine. A significant difference between the embodiments ofFIGS. 4 and 5 is that in the latter configuration a centrifugal, ratherthan an axial-flow, compressor, indicated at 66, is utilized in theinner spool" to offset the short blade lengths of the inner compressorand to take advantage of the fact that the flow is turned, in any event,in these embodiments. An advantage of the reversed flow embodiments ofthe present invention is that a shorter length machine is possible,which can be important in aircraft applications.

It will be understood, however, that in all such embodiments the use ofthe composite cycle enhances the machines overall efficiency. Thus,while various embodiments have been shown and described herein thisshould not be taken as a limitation of the invention and obviously otherturbomachinery arrangements will suggest themselves to those skilled inthe art in which my composite cycle will be of equal value.

What I desire to claim and secure by Letters Patent is:

l. A composite fluid flow turbomachine comprising:

a first compressor;

a second compressor, said second compressor being arranged tocontinuously receive a part only of the flow from said first compressor,

an inner duct surrounding said second compressor;

an outer duct surrounding said first compressor and said inner duct;means for injecting fuel within said outer duct and said inner duct forsupporting combustion therein downstream of said first compressor andsaid second compressor, respectively;

a first power turbine located in said inner duct and receiving anintegral fluid flow stream from said first and second compressors;

a second power turbine located partially in said outer duct, said secondpower turbine receiving a fluid flow stream from said first compressorand the integral fluid flow stream from said first and secondcompressors;

an outer driveshaft, said first power turbine and said second compressorbeing mounted on said outer driveshaft for rotation therewith;

an inner driveshaft concentric to said outer driveshaft, said secondpower turbine and said first compressor being mounted on said innerdriveshaft for rotation therewith;

and a power transfer turbine, said power transfer turbine being arrangedin series flow relation with said first and second power turbines, saidpower transfer turbine being mounted on said inner driveshaft andfurnishing power to help drive said first compressor, whereby theoverall cycle efficiency of said composite fluid flow turbomachine isincreased.

2. A composite fluid flow turbomachine comprising:

a first compressor;

a second compressor, said second compressor being arranged tocontinuously receive a part only of the flow from said first compressor;

an inner duct surrounding said second compressor;

an outer duct surrounding said first compressor and said inner duct;means for injecting fuel within said outer duct and said inner duct forsupporting combustion therein downstream of said first compressor andsaid second compressor, respectively;

a first power turbine located in said inner duct and receiving anintegral fluid flow stream from said first and second compressors;

a second power turbine located partially in said outer duct, said secondpower turbine receiving a fluid flow stream from said first compressorand the integral flow stream from said first and second compressors;

an outer driveshaft, said first power turbine and said second compressorbeing mounted on said outer driveshaft for rotation therewith;

an inner driveshaft concentric to said outer driveshaft, said secondpower turbine and said first compressor being mounted on said innerdriveshaft for rotation therewith mechanically free from the rotation ofsaid outer driveshaft;

and a power transfer turbine, said power transfer turbine being locatedin said inner duct downstream of said first power turbine, said powertransfer turbine being mounted on said inner driveshaft for rotationwith said first compressor and said second power turbine and furnishingpower to help drive said first compressor, whereby the overall cycleefficiency of said composite fluid flow turbomachine is increased.

3. A composite fluid flow turbomachine comprising:

a first compressor;

a second compressor, said second compressor being arranged tocontinuously receive a part only of the flow from said first compressor;

an inner duct surrounding said second compressor;

an outer duct surrounding said first compressor and said inner duct;

means for injecting fuel in said outer duct and said inner duct forsupporting combustion therein downstream of said first compressor andsaid second compressor, respectively;

a first power turbine located in said inner duct and receiving fluidflow from said first and second compressors;

a second power turbine located downstream of said first power turbine,said second power turbine extending transversely of both of said ductsfor receiving fluid flow from said first compressor through said outerduct and said first and second compressors through said inner duct;

and a power turbine, said power transfer turbine being located in saidinner duct downstream of said first power turbine, said power transferturbine rotating with said first compressor and said second powerturbine, the fluid effluent from said power transfer turbine mixing withthe flow from said first compressor and furnishing power to help drivesaid first compressor, whereby the overall cycle efficiency of saidcomposite fluid flow turbomachine is increased.

4. A composite fluid flow turbomachine comprising:

a first compressor;

a second compressor, said second compressor being arranged tocontinuously receive a part only of the flow from said first compressor;

an inner duct surrounding said second compressor;

an outer duct surrounding said first compressor and said inner duct;

means for injecting fuel in said outer duct and said inner duct forsupporting combustion therein downstream of said first compressor andsaid second compressor, respectively;

a first power turbine located in said inner duct and receiving flow fromsaid first and second compressors;

A second power turbine located downstream of said firs power turbine,said second power turbine extending transversely of both of said ductsfor receiving flow from said first compressor through said outer ductand said first and second compressors through said inner duct;

an outer driveshaft, said first power turbine and said second compressorbeing mounted on said outer driveshaft for rotation therewith;

an inner driveshaft concentric to said outer driveshaft, said secondpower turbine and said first compressor being mounted on said innerdriveshaft for rotation therewith;

and a power transfer turbine, said power transfer turbine being locatedin said inner duct downstream of said first power turbine, said powertransfer turbine being mounted on said inner driveshaft for rotationwith said first compressor and said second power turbine, the fluideffluent from said power transfer turbine mixing with the flow from saidfirst compressor downstream of said fuel injection means in said outerduct and furnishing power to help drive said first compressor, wherebythe overall cycle efficiency of said composite fluid flow turbomachineis increased.

5. A composite fluid flow turbomachine comprising:

a first compressor;

a second compressor, said second compressor being arranged tocontinuously receive a part only of the flow from said first compressor;

first and second duct means, said first duct means surrounding saidfirst and second compressors and said second duct means;

means for injecting fuel in said first and second duct means forsupporting combustion therein;

a first power turbine receiving flow from said second compressor andfurnishing driving energy thereto;

a second power turbine receiving flow from said first compressor andfurnishing driving energy thereto;

and a power transfer turbine, said power transfer turbine being locatedintermediate said first and second power turbines and receiving the flowfrom said first and second compressors through said second duct means,the fluid flow into said first power turbine and said power transferturbine being opposite in direction to the flow through said firstcompressor, and the fluid effluent from said power transfer turbinebeing turned 180 and mixing with the flow from said first compressorupstream of said fuel injection means in said outer duct and furnishingpower to help drive said first compressor, whereby the overall cycleefficiency of said composite fluid flow turbomachine is increased.

6. A composite fluid flow turbomachine comprising:

a first compressor;

a second compressor, said second compressor being arranged tocontinuously receive a part only of the flow from said first compressor;

an inner duct surrounding said second compressor;

an outer duct surrounding said first compressor and said inner duct;

means for injecting fuel in said outer duct and said inner duct forsupporting combustion therein downstream of said first compressor andsaid second compressor, respectively;

a first power turbine located in said inner duct and receiving anintegral fluid flow stream from said first and second compressors;

a second power turbine located in said outer duct and receiving a fluidflow stream from said first compressor and the integral flow stream fromsaid first and second compressors;

an outer driveshaft, said first power turbine and said second compressorbeing mounted on said outer driveshaft for rotation therewith;

an inner driveshaft concentric to said outer driveshaft, said secondpower turbine and said first compressor being mounted on said innerdriveshaft for rotation therewith mechanically free from the rotation ofsaid outer driveshaft;

and a power transfer turbine, said power transfer turbine being locatedin said inner duct downstream of said first power turbine, said powertransfer turbine being mounted on said inner driveshaft for rotationwith said first compressor and said second power turbine, the fluid flowinto said first power turbine and said power transfer turbine beingopposite in direction to the flow through said first compressor, and thefluid effluent from said power transfer turbine being turned and mixingwith the flow from said first compressor upstream of said fuel injectionmeans in said outer duct and furnishing power to help drive said firstcompressor, whereby the overall cycle efficiency of said composite fluidflow turbomachine is increased.

7. The invention as claimed in claim 6 wherein at least one of saidfirst and second compressors is of the centrifugal-flow type.

1. A composite fluid flow turbomachine comprising: a first compressor; asecond compressor, said second compressor being arranged to continuouslyreceive a part only of the flow from said first compressor, an innerduct surrounding said second compressor; an outer duct surrounding saidfirst compressor and said inner duct; means for injecting fuel withinsaid outer duct and said inner duct for supporting combustion thereindownstream of said first compressor and said second compressor,respectively; a first power turbine located in said inner duct andreceiving an integral fluid flow stream from said first and secondcompressors; a second power turbine located partially in said outerduct, said second power turbine receiving a fluid flow stream from saidfirst compressor and the integral fluid flow stream from said first andsecond compressors; an outer driveshaft, said first power turbine andsaid second compressor being mounted on said outer driveshaft forrotation therewith; an inner driveshaft concentric to said outerdriveshaft, said second power turbine and said first compressor beingmounted on said inner driveshaft for rotation therewith; and a powertransfer turbine, said power transfer turbine being arranged in seriesflow relation with said first and second power turbines, said powertransfer turbine being mounted on said inner driveshaft and furnishingpower to help drive said first compressor, whereby the overall cycleefficiency of said composite fluid flow turbomachine is increased.
 2. Acomposite fluid flow turbomachine comprising: a first compressor; asecond compressor, said second compressor being arranged to continuouslyreceive a part only of the flow from said first compressor; an innerduct surrounding said second compressor; an outer duct surrounding saidfirst compressor and said inner duct; means for injecting fuel withinsaid outer duct and said inner duct for supporting combustion thereindownstream of said first compressor and said second compressor,respectively; a first power turbine located in said inner duct andreceiving an integral fluid flow stream from said first and secondcompressors; a second power turbine located partially in said outerduct, said second power turbine receiving a fluid flow stream froM saidfirst compressor and the integral flow stream from said first and secondcompressors; an outer driveshaft, said first power turbine and saidsecond compressor being mounted on said outer driveshaft for rotationtherewith; an inner driveshaft concentric to said outer driveshaft, saidsecond power turbine and said first compressor being mounted on saidinner driveshaft for rotation therewith mechanically free from therotation of said outer driveshaft; and a power transfer turbine, saidpower transfer turbine being located in said inner duct downstream ofsaid first power turbine, said power transfer turbine being mounted onsaid inner driveshaft for rotation with said first compressor and saidsecond power turbine and furnishing power to help drive said firstcompressor, whereby the overall cycle efficiency of said composite fluidflow turbomachine is increased.
 3. A composite fluid flow turbomachinecomprising: a first compressor; a second compressor, said secondcompressor being arranged to continuously receive a part only of theflow from said first compressor; an inner duct surrounding said secondcompressor; an outer duct surrounding said first compressor and saidinner duct; means for injecting fuel in said outer duct and said innerduct for supporting combustion therein downstream of said firstcompressor and said second compressor, respectively; a first powerturbine located in said inner duct and receiving fluid flow from saidfirst and second compressors; a second power turbine located downstreamof said first power turbine, said second power turbine extendingtransversely of both of said ducts for receiving fluid flow from saidfirst compressor through said outer duct and said first and secondcompressors through said inner duct; and a power turbine, said powertransfer turbine being located in said inner duct downstream of saidfirst power turbine, said power transfer turbine rotating with saidfirst compressor and said second power turbine, the fluid effluent fromsaid power transfer turbine mixing with the flow from said firstcompressor and furnishing power to help drive said first compressor,whereby the overall cycle efficiency of said composite fluid flowturbomachine is increased.
 4. A composite fluid flow turbomachinecomprising: a first compressor; a second compressor, said secondcompressor being arranged to continuously receive a part only of theflow from said first compressor; an inner duct surrounding said secondcompressor; an outer duct surrounding said first compressor and saidinner duct; means for injecting fuel in said outer duct and said innerduct for supporting combustion therein downstream of said firstcompressor and said second compressor, respectively; a first powerturbine located in said inner duct and receiving flow from said firstand second compressors; A second power turbine located downstream ofsaid first power turbine, said second power turbine extendingtransversely of both of said ducts for receiving flow from said firstcompressor through said outer duct and said first and second compressorsthrough said inner duct; an outer driveshaft, said first power turbineand said second compressor being mounted on said outer driveshaft forrotation therewith; an inner driveshaft concentric to said outerdriveshaft, said second power turbine and said first compressor beingmounted on said inner driveshaft for rotation therewith; and a powertransfer turbine, said power transfer turbine being located in saidinner duct downstream of said first power turbine, said power transferturbine being mounted on said inner driveshaft for rotation with saidfirst compressor and said second power turbine, the fluid effluent fromsaid power transfer turbine mixing with the flow from said firstcompressor downstream of said fuel injection means in said outer ductand furnishing power to help drive said first compressor, whereby theoVerall cycle efficiency of said composite fluid flow turbomachine isincreased.
 5. A composite fluid flow turbomachine comprising: a firstcompressor; a second compressor, said second compressor being arrangedto continuously receive a part only of the flow from said firstcompressor; first and second duct means, said first duct meanssurrounding said first and second compressors and said second ductmeans; means for injecting fuel in said first and second duct means forsupporting combustion therein; a first power turbine receiving flow fromsaid second compressor and furnishing driving energy thereto; a secondpower turbine receiving flow from said first compressor and furnishingdriving energy thereto; and a power transfer turbine, said powertransfer turbine being located intermediate said first and second powerturbines and receiving the flow from said first and second compressorsthrough said second duct means, the fluid flow into said first powerturbine and said power transfer turbine being opposite in direction tothe flow through said first compressor, and the fluid effluent from saidpower transfer turbine being turned 180* and mixing with the flow fromsaid first compressor upstream of said fuel injection means in saidouter duct and furnishing power to help drive said first compressor,whereby the overall cycle efficiency of said composite fluid flowturbomachine is increased.
 6. A composite fluid flow turbomachinecomprising: a first compressor; a second compressor, said secondcompressor being arranged to continuously receive a part only of theflow from said first compressor; an inner duct surrounding said secondcompressor; an outer duct surrounding said first compressor and saidinner duct; means for injecting fuel in said outer duct and said innerduct for supporting combustion therein downstream of said firstcompressor and said second compressor, respectively; a first powerturbine located in said inner duct and receiving an integral fluid flowstream from said first and second compressors; a second power turbinelocated in said outer duct and receiving a fluid flow stream from saidfirst compressor and the integral flow stream from said first and secondcompressors; an outer driveshaft, said first power turbine and saidsecond compressor being mounted on said outer driveshaft for rotationtherewith; an inner driveshaft concentric to said outer driveshaft, saidsecond power turbine and said first compressor being mounted on saidinner driveshaft for rotation therewith mechanically free from therotation of said outer driveshaft; and a power transfer turbine, saidpower transfer turbine being located in said inner duct downstream ofsaid first power turbine, said power transfer turbine being mounted onsaid inner driveshaft for rotation with said first compressor and saidsecond power turbine, the fluid flow into said first power turbine andsaid power transfer turbine being opposite in direction to the flowthrough said first compressor, and the fluid effluent from said powertransfer turbine being turned 180* and mixing with the flow from saidfirst compressor upstream of said fuel injection means in said outerduct and furnishing power to help drive said first compressor, wherebythe overall cycle efficiency of said composite fluid flow turbomachineis increased.
 7. The invention as claimed in claim 6 wherein at leastone of said first and second compressors is of the centrifugal-flowtype.